Due to special optical characteristics of cholesteric liquid crystals (LCs), cholesteric liquid crystals can be used to manufacture a reflective liquid crystal display (LCD) device. As shown in FIG. 10, directors of the cholesteric liquid crystals are distributed helically due to the different directors of layers of the cholesteric liquid crystals. Thickness of an LC molecular layer required by rotation of the directors by 360 degrees is known as an optical rotatory thickness (pitch). Right-hand optical rotatory cholesteric LCs reflect left-hand circularly polarized light and pierce through right-hand circularly polarized light, so that the reflected light is still the left-hand circularly polarized light. Left-hand optical rotatory cholesteric LCs reflect the right-hand circularly polarized light and pierce through the left-hand circularly polarized light so that the reflected light is still the right-hand circularly polarized light.
As shown in FIG. 11 and FIG. 12, the cholesteric LCs generally used in manufacture of the reflective LCD device. There are mainly two working patterns: one is the LC molecules are kept in a reflective state of a planar structure, and the second is the LC molecules are kept in a scattering state of a focal conic structure. The two states can be realized by applying voltage on both sides of the LC layer to form a control switch to control the reflective state and the scattering state of the cholesteric LCs.
The cholesteric LCD device also mainly has two structures. FIG. 11 shows a first structure: red (R), green (G), and blue (B) cholesteric LCs are used and made into picture elements in a panel 20 (cell). A black absorption layer 21 is arranged below the panel. When the cholesteric LCD device displays white, R, G, and B cholesteric LCs all reflect corresponding colors. When the cholesteric LCD device displays colors the color (e.g. red) to be displayed is reflected, and other colors (e.g. green and blue) are pierce through the color (e.g. red) that is displayed. When the cholesteric LCD device displays black, R, G, and B picture elements do not reflect, and all light is absorbed by the black absorption layer 21. FIG. 12 shows a second structure: three layers of the panels 20 (cell) are manufactured. Each of the layers of the panel 20 is made with cholesteric LCs that controls three colors (R, G, and B). A black absorption layer 21 is arranged below the panel 20. When the cholesteric LCD device displays the white, R, G, and B cholesteric LCs all reflect corresponding colors. When the cholesteric LCD device displays the colors, the color (e.g. red) to be displayed is reflected, and other colors (e.g. green and blue) are pierce through the color (e.g. red) that is displayed. When the cholesteric LCD device displays the black, R, G, and B picture elements do not reflect, and all light is absorbed by the black absorption layer 21.